1. Field of the Invention
This invention relates to a permanent magnet consisting of an iron-palladium or iron-palladium-silver alloy with small amount of less than 0.5 atomic % of impurities and a method of producing the same. An object of the invention is to provide a permanent magnet which is easily workable and has a high coercive force and a large maximum energy product.
2. Description of the Prior Art
As a conventional permanent magnet using the .alpha.-.gamma.' transformation, there is a permanent magnet made of Vicalloy (trademark) which is a 52% cobalt-9.5% vanadium-iron system alloy. This system alloy has a .gamma. phase at a high temperature and an .alpha.+.gamma.' phase of ordered lattice at room temperature. Accordingly, when this alloy is subjected to water quenching and then cold working, the .gamma. phase is transformed into .alpha. phase, and upon tempering, a part of the .alpha. phase is transformed into fine .gamma.' phase and precipitated as dispersion precipitations, whereby the coercive force thereof is increased. However, the coercive force of the Vicalloy magnet is generally small; namely, its maximum value of coercive force is 500 Oe, and in order to achieve this value of coercive force, a forced cold working of up to about 98% is necessary. Besides, this alloy contains an easily oxidizable element, i.e., vanadium, so that this alloy has short-comings in that in its melting process it is difficult to avoid oxidation and the process of making the permanent magnet from the alloy is complicated.
As an alloy wherein .gamma. phase is transformed in .alpha.+.gamma..sub.1 phase during cooling, an iron-palladium alloy is known. The magnet characteristics of this alloy were disclosed by Kussmann and Muller in "Zeitschrift fur angewandte physik" 1964, Volume 17 Number 7, pages 509-511. It was found that when an alloy consisting of 18 of 50 atomic % of palladium and the remainder of iron was quenched from 1,000.degree. C. and tempered at 450.degree. C., the coercive force of the alloy was increased up to 780 Oe. The aforementioned disclosure refers to the coercive force in the main, but it does not provide any detailed description of other magnetic characteristics such as residual magnetic flux density and the maximum energy product.